Return flow carburetor



Aug. 24, 1965 T. M. BALL 3,2024% RETURN FLOW GARBURETOR Original Filed June 5, 1959 INVENTOR. mamas ME Z for example.

United States Patent 3,262,4tl3 RETURN FLOW CARBURETOR Thomas M. Ball, Bloomfield Hills, Mich assignor to Chrysler Corporation, Highland Parlr, Mich, a corporation of Delaware Original applications June 5, E59, Ser. No. $18,349, now Patent No. 3,ii8,88b', dated .l uiy 23, E363, and Mar. 23, 1961, Ser. No. 97,775, new Fatent No. 3,127,454, dated Mar. 31, 1964. Divided and this application Jan. 36, 1363, Ser. No, 254,875

3 Claims. ((11. 261-36) This invention relates to improvements in a carburetor particularly adapted for use with an automobile internal combustion engine and is a division of my copending applications Serial No. 818,349, filed June 5, 1959, now Patent Number 3,698,885, issued June 23, 1963, and Serial No. 97,775, filed March 23, 1961, now Patent Number 3,127,454, issued March 31, 1964.

In conventional carburetors, a float controlled fuel inlet needle valve is employed to regulate the fuel level in the carburetor fuel bowl. Small dirt particles sometimes interfere with effective operation of the valve, as for example by becoming lodged between mating valve seats which otherwise cooperate to regulate the fuel flow into the fuel bowl. Also the floats require considerable size in order to be effective because of the comparatively low specific gravity of the fuel. In consequence the size of the fuel bowl must be appreciably larger than is otherwise desired.

An important object of the present invention is to provide an improved carburetor which avoids the foregoing objections and in particular to provide a floatless carburetor which does not require a fuel inlet needle valve.

Another obiect is to provide such a construction including an overflow standpipe in the fuel bowl having an upper opening which determines the maximum fuel level in the bowl. A fuel inlet pump is provided to pump fuel into the bowl at a rate in excess of demand. The excess fuel overflows into the standpipe and is returned to th fuel tank. In order to overcome adverse grade conditions which prevent the excess fuel from returning to the tank by gravity flow, a scavenging pump is provided in the fuel return line between the overflow standpipe and the tank.

Among other advantages of the above structure, elimination of the necessarily large float enables utilization of a comparatively small fuel bowl closely adjacent the inlet air induction conduits of a multiple barrel carburetor, The small fuel bowl thus located is less sensitive to grade and inertia effects and enables uniform fuel distribution to each of the several induction conduits. lso recirculation of the fuel drives off its more volatile fuel fractions and thereby minimizes some of the problems of the conventional float controlled carburetor, as for example those concerned with vapor formation.

In order to provide adequate fuel during maximum engine speed at wide open throttle, a fuel inlet pump is provided which delivers an excess supply of fuel to the fuel bowl during all operating conditions of the engine. When the throttle is suddenly closed while the engine is still operating at high speed, unless some provision is made to the contrary, approximately 98% of the fuel supplied to the fuel bowl will be recirculated, whereas approximately only 2% of the fuel will be used by the engine. In general the life of a fuel pump and in particu lar the life of an engine driven diaphragm type pump, which is preferred for supply fuel in the quantity re quired and at a substantially uniform pressure regardless of changes in engine speed, depends upon the quantity of fuel pumped.

For the above reasons, as well as the desirability of conserving power in an automobile engine and of minimizing fuel heating by excessive recirculation, another object of the present invention is to provide improved simple and highly effective means for supplying fuel to the fuel bowl in reasonable and safe amounts related to engine requirements.

Another object is to provide a bypass conduit which extends from the discharge side of the fuel supply pump to the inlet side of the pump and which contains a suitable valve adjustable in response to variations in engine load for controlling the fuel flow in the bypass conduit.

Other objects of this invention will appear in the following description and appended claims, reference being bad to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a schematic mid-sectional view of a return flow carburetor and pump embodying the present invention.

FIGURE 2 is a view similar to FIGURE 1 illustrating a modification.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to FIGURE 1, the carburetor shown comprises a cast housing formed to provide an air inlet induction conduit including a venturi portion it) having a restricted venturi if at its upper portion and a throttle blade 12 pivotally mounted on a shaft 13 at a lower portion usually referred to as the throttle body. An upper portion of the casting is formed to provide an air born 14 adapted to be connected with the usual air filter and opening at its downstream end into the venturi 11 to supply air thereto. The casting portions ill and 14 are suitably secured together, as for example by screws not shown, and comprise an upper portion of the air inlet and fuel mixing induction system which extends downstream of the throttle valve 12 and discharges into the usual engine cylinders in a conventional manner.

Integral with the casting lit in the present instance is a fuel bowl casting 15 containing an annular chamber or fuel bowl 116 enclosing a cylindrical standpipe or weir 17 which also serves as an acceleration pump cylinder containing a plunger 18 reciprocable in its lower portion and secured to a plunger shaft 19 for actuation thereby. Where desired the shaft 19 is connected by suitable linkage with a pedal operated accelerator mechanism. which controls the opening and closing of valve 12 to operate conjointly therewith. Upon upward movement of plunger 18, fuel is drawn into the lower portion of chamber 17 via conduit 29 in communication with the bowl 16. A suitable check valve illustrated schematically as a ball check element 21 normally seats at the mouth of the duct 26 opening into the lower portion of chamber 17 to prevent loss of fuel therefrom but is raised from its seat by the fuel flow into chamber 17 on the upstroke of plunger 18. Upon downward movement of plunger 18 the fuel is forced from chamber 17 into the induction conduit via acceleration fuel conduit 22, ball check valve 23, and nozzle 24 which latter discharges into the induction conduit at a location immediately above the throat of venturi 11. The check valve 23 is schematically illustrated as a ball normally urged by a spring to a seated position 0 closing nozzle 24 from the interior of chamber 17, the

ball being readily movable upward against the tension of its seating spring by the acceleration fuel pressure upon downward movement of plunger 18. The main Y16 and communicates at its upper end witha fuel nozzle 27 having its discharge orifice located within the throat of venturi 11. f

In accordance with the structure described thus far, fuel entering the bowl 16 in excess of engine requirements overflows the upper edge 'of standpipe 17 which thereby maintains the fuel in the bowl 16 at a predetermined maximum level determined by the effective height of the standpipe 17 without recourse to a float operated mechanism. Fuelis supplied to the bowl 16 from a suitable fuel tank via conduit 28. p

A multiple piece fuel pump housing 37 comprising an upper dome 38 and a lower basin 39 cooperate with diaphragrns 40 and 41 respectively to provide an inlet fuel pumping or working'chamber 42 and an exhaust fuel pumping or scavenging chamber 43. Springs 44 and 45 under compression between portionsof housing 37 and diaphragms 40 and 41 respectively urgethe former dia phragmupwardly and the latter diaphragm downwardly to effect-the pumpingstrokes for the respective chambers 42 and 43. I v

The upper working-chamber 42 comprises a portion of supply duct 28 whichcommunicates upstream'of chamber 42 with the fuel tank 28b. Fuel enters and leaves 'chamber 42 via an inlet 'port 46 and a discharge port 47 associated with check valves 48 and 49 respectively. Upon downward movement of diaphragm 40 as explained below, fuel is drawn in the direction of the arrow 28a from the tank and-through inlet port 46 into working chamber ;42. During this operation ball valve 48 is forced fromv its seat at port 46 by the fuel flow, and ball 'valve49- seats at the discharge port 47 to close'the latter "from the fuel bowl 16. Upon upward movement of dia 'phragm 40, ball valve, 48 is caused to seat at port 46 to close the working chamber '42 from the fuel tank. During this operation, the pressure exerted in chamber 42 unseats ball valve-49 from port 47 and supplies fuel via conduit 28 to the fuel bowl 16. a The spaces at the sides of pumping chamber 42 may be considered part of the fuel return system or means. Upstream, the conduit 52 communicates with standpipe 17 at a location above the uppermost limit of movement of plunger 18. The return fuel enters chamber 43 via port 53 and discharges from chamber 43 via port 54. 'Ball check valves 55 and 56 are associated with ports 53 and 54 respectively; so that of thediaphragms 40 and 41 opposite chambers 42 and :Videdwvhich communicates at opposite ends with the discharge and inlet sides of chamber 42 respectively at lo "cations downstream ofport 47 andupstream of 'port 46. "Avalving port or orifice 29 in conduit'42a is controlled 'bya taperedneedle valve 31registering'with port 29 at the latters high pressure side and connected to the underside of a flexible diaphragm 32. Upon downward .movement of valve 31, orifice 29 is progressively restricted to reduce the fuel flow therethrough as described below." The diaphragm 32 is confined within a pressure chamber 33 and. partitions the latter into upper andlower parts. A coil spring 34 in the upper chamber. part under compressionbetween diaphragm 32 and housing 33 normally .urg es diaphragm32 with the connected'valve 31 downwardly to maintain orifice29 closed. The chamber part above diaphragm32 is connected by a pressure duct 35 to theinductioncohduit at a point adjacent and downstream of the throttle valve 12. Inorder to facilitate operation of thediaphragm 32, the lower ichamber part overflow fuel from standpipe 17' to the inlet side of pumpin gchamber 42, the three elements comprising conduit :52,'fuel tank 28b, andthe portion of .c'onduitZS upstream upon upward movement of diaphragm 41 as described below, ball 56 seats against port 54 to close chamber 43 from the fuel tank. During this operation, ball 55 is unseated from port 53 to open communication between chamber 43 and standpipe' 17 and to draw fuel from the latter. Upon downward movement of diaphragm 41, ball 55 is seated against port 53 to close chamber 43 from standpipe 17. Simultaneously ball 56 is unseated. from port 54 by the pressure in chamber 43 to discharge fuel from the latter in the, direction of arrow 52a to the tank. Movement limiting pins in the conduits 28 and 52 associated with the'ball valves 48, 49, 55 and 56 prevent undue movement of the balls from their associated ports. Inasmuch as the check valves are well known, these are merely shown schematically and are not discussed in further detail. V V i Actuation of the diaphragm. 40 and 41 is accomplished by driving shafts 57 and 58 connected to these dia phragms and terminating in enlarged heads 59 and 60 respectively. Pivotal levers 61 and 62 are pivoted on housing 37 at locations 63 and 64' respectively between their ends. Each lever has one end engaged with a rotating eccentric cam 65 mounted on a shaft 66 driven by the automobile engine. The opposite ends of the levers 61'and 62 are provided with oversiz'ed openings 67 and 68 through which the rods 57 and 58 extend freely to enable their relative sliding movement with respect to the levers 61 and 62 until the levers engage the enlarged heads 59 and 6d.

Upon operation of the automobile engine, shaft 66 is rotated to turn eccentric cam 65 and thereby cause pivot ing of levers 61 and 62, Upon clockwise pivoting of lever 61, or counterclockwise pivoting of lever 62, the head 59 or 66 is engaged to pull the associated rod 57 and 58 in the direction to compress the spring'44 and J 45 as the case might be. Uponcounterclockwise pivoting of lever 61 and clockwise pivoting of lever 62, the

oversized openings 67 and 68 enable the levers to swing independently of the shafts 57 and 58, whereupon springs 44 and 45 are released to force diaphragms'42 and 43 in pumping actions toward the associated dome 38 or basin 39. The pivotal action of levers 61 and 62 merely compresses the springs 44 and 45 alternately, which latter then '17 and returns by conduit 52 to chamber 43 via port .53,

whereupon the fuel is pumped to the fuel tank by down- Ward spring urged pumping'movement of diaphragm 41.

Variations in. engine fuel requirements are detected by conduit '35 which progressively increases the pressure in chamber33 above diaphragm 32 as valve 12 is pivoted .toward a wide open position, i.e., as engine load increases.

The increased pressure in chamber 33, in cooperation with spring 34, urges diaphragm 32 and valve 31' downward,

thereby to increasethe restriction at orifice 29. In consequence the'bypass fuel flow through orifice 29 is decreased with increasing engine load and the fuel flow through conduit 28 to bowl 16 is increased; i

' In'the converse action, as throttle valve 12 moves toward its closed position shown, the pressure below valve -12 and accordingly. the pressure in chamber 33 above diaphragm 32 decreases, enabling atrnospheric pressure on the underside of diaphragm 32 to urge the latter upward against the tension of spring 34 and cause valve 31 to decrease the restriction of orifice 29. Thus with de creasing engine load, the fuel flow in the bypass conduit 42a increases, the fuel flow to bowl 16 is decreased, and recirculation of fuel through bowl 16 is minimized. In this regard the resistance to fuel flow in conduit 28 downstream of bypass conduit 42a is preferably greater than the corresponding resistance in bypass conduit 42a and is predetermined, as for example by a restricted orifice 3b, in order to assure adequate fiuid flow in bypass conduit 42:: when valve 31 opens.

Although the structure of FIGURE 1 provides means for supplying fuel to bowl 16 at a rate which is a function of engine load, the vacuum induced force below valve 12 is at its maximum at low engine load and progressively decreases as engine load increases. Accordingly, at comparatively high engine load when the throttle valve 12 is open fully or nearly so, that vacuum force acting on diaphragm 32 is a minimum and changes in the throttle position result in comparatively low magnitude pressure changes on diaphragm 32.

Where increased effectiveness of the vacuum induced force at high engine load is desired, a construction such as illustrated in FIGURE 2 is preferred. The general arrangement of the return flow carburetor and pump is the same in FIGURE 2 as in FIGURE 1 so that identical parts are numbered the same in both drawings. The distinction of FIGURE 2 is that conduit 35 is replaced by conduit 69, and needle valve 31 is replaced by a tapered valve 7:) registering with the low pressure side of orifice 29 and having a stem secured to diaphragm 32. Conduit 69 connects chamber 33 above diaphragm 32 with the induction conduit at a location adjacent the throat of the venturi 11. Accordingly as engine load increases, the vacuum induced force at the throat of venturi 11 increases and becomes a maximum at wide open throttle. The resulting low pressure above diaphragm 32 enables the atmospheric pressure on the underside of the diaphragm to urge the latter upwardly against the force of spring 34 and move valve 70 toward orifice 29 to increase the restiiction thereof. In consequence, as the airflow through the venturi throat 11 increases with increasing engine load, the fuel flow through bypass orifice 29 decreases and the fuel flow into bowl 16 increases. Conversely as airflow through venturi throat 11 decreases with decreasing engine load, the vacuum induced force above diaphragm 32 decreases, enabling spring 34 to move valve 7% downwardly and decrease the restriction at orifice 29, thereby to increase the bypass how in conduit 42a and to reduce the fuel flow into bowl 16.

In the FIGURE 2 construction, the vacuum induced force at the throat of venturi 11 becomes a minimum at low engine load. Accordingly where desired a dual control of the inlet fuel flow as illustrated in both FIGURES 1 and 2 may be employed to assure adequate operating force during conditions of both high and low engine loads.

Having thus described the invention, I claim:

1. In a carburetor for an internal combustion engine having a fuel and air induction system, a fioatless fuel bowl, duct means connecting said bowl and system, a fuel pump having an inlet and an outlet, first conduit means connecting said outlet with said fuel bowl for supplying fuel to the latter upon operation of said pump, means for maintaining the fuel in said bowl at a predetermined level comprising an overflow weir in said bowl defining at least in part a chamber adapted to receive excess fuel overflowing said weir from said boWl when the fuel in said bowl attains said predetermined level, fuel return means for returning excess fuel from said chamber to said inlet including a fuel return conduit in communication with said chamber to drain fuel therefrom upon overflow of excess fuel thereinto from said bowl, means for diverting a portion of the fuel in said first conduit means from said fuel bowl and system including bypass conduit means connecting said first conduit means with said fuel return means, means for proportioning the fuel flow from said fuel pump to said bowl and bypass conduit means including a predetermined restriction in said first conduit means at a location between said bowl and the connection of said bypass conduit means with said first conduit means, said means for proportioning also including valve means in said bypass conduit means for controlling fuel flow in the latter, and means responsive to engine load for adjusting said valve means comprising means responsive to changes in the air flow in said system and operably connected with said valve means for adjusting the latter to increase the fuel flow in said first conduit means to said fuel bowl with increasing air flow.

2. The combination in a carburetor in accordance with claim 1, said induction system having a venturi throat therein, and said means responsive to changes in said air flow being responsive to said changes at said venturi throat.

3. The combination in a carburetor in accordance with claim 1, said means responsive to changes in said air flow being responsive to said changes at a location downstream of said throttle valve.

References Cited by the Examiner UNITED STATES PATENTS 1,881,860 10/32 Muzzy 261-36 2,136,959 11/38 Winfield 26136 2,409,965 10/46 Udale 26136 2,691,509 10/54 Rivoche 261-36 2,874,944 2/59 Dolza 261-36 3,127,453 3/64 Sarto 26l--36 HARRY B. THORNTON, Primary Examiner.

HERBERT L. MARTIN, Examiner. 

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING A FUEL AND AIR INDUCTION SYSTEM, A FLOATLESS FUEL BOWL, DUCT MEANS CONNECTING SAID BOWL AND SYSTEM, A FUEL PUMP HAVING AN INLET AND AN OUTLET, FIRST CONDUIT MEANS CONNECTING SAID OUTLET WITH SAID FUEL BOWL FOR SUPPLYING FUEL TO THE LATTER UPON OPERATION OF SAID PUMP, MEANS FOR MAINTAINING THE FUEL IN SAID BOWL AT A PREDETERMINED LEVEL COMPRISING AN OVERFLOW WEIR IN SAID BOWL DEFINING AT LEAST IN PART A CHAMBER ADAPTED TO RECEIVE EXCESS FUEL OVERFLOWING SAID WEIR FROM SAID BOWL WHEN THE FUEL IN SAID BOWL ATTAINS SAID PREDETERMINED LEVEL, FUEL RETURN MEANS FOR RETURNING EXCESS FUEL FROM SAID CHAMBER TO SAID INLET INCLUDING A FUEL RETURN CONDUIT IN COMMUNICATION WITH SAID CHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OF EXCESS FUEL THEREINTO FROM SAID BOWL, MEANS FOR DIVERTING A PORTION OF THE FUEL IN SAID FIRST CONDUIT MEANS FROM SAID FUEL BOWL AND SYSTEM INCLUDING BYPASS CONDUIT MEANS CONNECTING SAID FIRST CONDUIT MEANS WITH SAID FUEL RETURN MEANS, MEANS FOR PROPORTIONING THE FUEL FLOW FROM SAID FUEL PUMP TO SAID BOWL AND BYPASS CONDUIT MEANS INCLUDING A PREDETERMINED RESTRITION IN SAID FIRST CONDUIT MEANS AT A LOCATION BETWEEN SAID BOWL AND THE CONNECTION OF SAID BYPASS CONDUIT MEANS WITH SAID FIRST CONDUIT MEANS, SAID MEANS FOR PROPORTIONING ALSO INCLUDING VALVE MEANS, IN SAID BYPASS CONDUIT MEANS FOR CONTROLLING FUEL FLOW IN THE LATTER, AND MEANS RESPONSIVE TO ENGINE LOAD FOR ADJUSTING SAID VALVE MEANS COMPRISING MEANS RESPONSIVE TO CHANGES IN THE AIR FLOW IN SAID SYSTEM AND OPERABLY CONNECTED WITH SAID VALVE MEANS FOR ADJUSTING THE LATTER TO INCREASE THE FUEL FLOW IN SAID FIRST CONDUIT MEANS TO SAID FUEL BOWL WITH INCREASING AIR FLOW. 